攻角与马赫数对进气道起动影响的可比拟性

Analogy Between Effects of Attack Angle and Mach Number on Inlet Starting

关键词:  高超声速进气道  自起动  数值模拟  激波风洞  攻角

Key words:  Hypersonic inlet  Self-starting  Numerical simulation  Shock tunnel  Angle of attack

摘要:

针对高速风洞变来流马赫数的能力有限，不易获得高超声速进气道起动马赫数界限的问题，本文尝试通过改变进气道模型攻角的方法来模拟来流马赫数的变化，分析定来流马赫数变攻角与定攻角变来流马赫数两种途径下二元进气道起动性能之间的关系，以助于风洞实验获得进气道的起动马赫数界限。结果表明，在Ma∞=5.9来流条件下，进气道不起动和自起动的临界攻角分别在12°～13°和0°～1°。定来流马赫数变攻角与定攻角变来流马赫数两种途径下，进气道不起动和自起动临界所对应的内收缩段入口马赫数基本一致。对于同一内收缩段入口马赫数，当变攻角跨度小于4°时，两种路径下进气道的内部流场与壁面压力分布规律符合较好；当变攻角跨度较大时，两者的差别也增大。对于二元高超声速进气道模型，当常规风洞的来流马赫数在进气道起动边界附近时，在一定的攻角范围内，可以尝试通过攻角机构连续改变模型安装攻角的办法来模拟变马赫数引起的进气道起动特性的演变过程。

Abstract:

Since the ability of changing flow Mach number in high speed wind tunnels is limited，the boundary of the inlet starting Mach number cannot be obtained easily. Studies are conducted in the present paper to help the wind tunnel experiments to obtain the boundary of the inlet starting ability and to verify that the cases of different freestream Mach numbers can be simulated by changing the attack angle of the inlet model. The correlations between changing the attack angle at a specific freestream Mach number and changing the freestream Mach number at a specific attack angle which affect the starting performance of the 2-D hypersonic inlet are investigated. The results show that the critical attack angle of unstarting and self-starting of the inlet at Ma∞=5.9 flow are in the range of 12°～13° and 0°～1°，respectively. It is found that the effective flow Mach numbers at the entrance of the inner contraction of the 2-D inlet are reasonably consistent at the unstarting limit and the self-starting limit，either by changing attack angles or by changing freestream Mach numbers. Moreover，for the same effective flow Mach number at the entrance of the inner contraction，when the variation range of the attack angle is less than 4 o，the inner flow field and the wall pressure distribution obtained by the two methods are similar，otherwise the differences are very apparent. This indicates that for 2-D hypersonic inlets，when the Mach number of a conventional wind tunnel is near the boundary of the inlet starting ability，one can try to simulate the cases of different freestream Mach numbers by changing the attack angle within a certain range in wind tunnels to obtain the inlet starting behaviors.